The OLED (Organic Light Emitting Diode) as a type of current-type light emitting devices is more and more applied to high performance display areas due to its characteristics such as self light emitting, fast response, wide angle of view, capability of being fabricated on a flexible substrate, and so on. The OLED can be classified into two kinds in terms of driving manner, which are PMOLED (Passive Matrix Driving OLED) and AMOLED (Active Matrix Driving OLED). For the conventional PMOLED, the driving time for a single pixel usually needs to be reduced with the increase of the size of the display apparatus; therefore, the transient current needs to be increased, causing dramatic increase of power consumption. However, in the AMOLED technology, current is input into each OLED through progressive scanning by a TFT (Thin Film Transistor) switch circuit, which can solve the above problems well.
In existing AMOLED panels, the TFT switch circuits mostly use low temperature poly silicon (LTPS) TFTs or oxide TFTs. In contrast to a normal amorphous-Si TFT, the LTPS TFT and the Oxide TFT have higher mobility and more stable characteristics, and are more suitable to be applied in the AMOLED display. However, due to the limitation of crystallization process and fabrication level, TFT switch circuits fabricated on a large area glass substrate usually show nonuniformity in electrical parameters such as threshold voltage, mobility or the like, such that the threshold voltages of the respective TFTs deviate differently, which results in current difference and brightness difference of the OLED display devices that can be perceived by human eyes. In addition, the threshold voltage of the TFT will shift under long time pressure and high temperature. The threshold shift amount of TFTs in different parts of the panel is different due to different display pictures, causing difference in display brightness. Because such a difference is related to the image displayed previously, it is usually presented as the afterimage phenomenon.